BZ 220 Final part 1
Morphospecies Concept
-Distinct morphological differences -subset of phylogenetic species concept
Postmating Barriers
-Gametic Mortality -Zygotic Mortality -Hybrid Inviability -Hybrid Sterility
What types of characters are used to recognize monophyletic, paraphyletic, polyphyletic groups?
-Monophyletic are identified by synapomorphies -Paraphyletic groups are identified by synapomorphies and Symplesiomorphies (or reversals) -Polyphyletic groups are identified by convergences
Premating Barriers
-Seasonal and habitat Isolation -Ethological Isolation (behavioral)
How is a preferred phylogeny identified using parsimony with multiple characters?
-The most parsimonious pattern of character-state change is noted for each character separately, for each tree -The number of changes is summed across characters for each tree -The preferred tree is the one that implies the fewest overall character-state changes, minimizing ad hoc hypotheses (i.e., convergences, reversals)
Phylogenetic Species Concept
-diagnosable by a unique combination of character states -smallest aggregation of sexual populations or asexual lineages diagnosable by a fixed, unique combination of character states in comparable individuals -Examples of Character States →Single DNA substitution →Major Morphological Change →Behavioral Difference
What are characters states that the phylogenetic species concept can use to identify distinct species?
-fixed, unique conbination of character states in comparable individuals -Single DNA substitution -Major morphological change -Behavioral difference
Allopatric Speciation
-geographic isolation of populations →Dispersal-individual(s) cross barriers →Vicariance- new barrier separated pre-existing populations
Convergence
-morphological similarities -occurs when natural selection favors similar structures as solutions to problems posed by similar environments -If convergent evolution has occurred, then similar traits are not homologous and do not qualify as synapomorphies
Biological Species Concept
-reproductive isolation -a group of interbreeding organisms that are reproductively isolated from all other such groups -"interbreeding"=successfully producing fertile offspring -legal definition of species for Endangered Species Act
Sympatric Speciation
-speciation without geographical isolation →food source →host specificity →timing of reproduction
How ware phylogenies used to test hypotheses of adaptation and the order of evolutionary changes?
-used to establish order of events in which changes took place -can optimize and "character" onto a tree, regardless of whether it is heritable or not
Parsimony Informative
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Parsimony Uninformative
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What is an independent evolutionary lineage?
An independent evolutionary lineage is a species.
How do each of the three species concepts differ from each other? (consider all 3)
Unlike the others the Biological Species Concept only refers to sexual species and reproductive isolation. The Phylogenetics Species Concept refers to asexual and sexual species and focusses on a unique combination of character states. The Morphospecies Concept focusses on distinct morphological differences
What are the character states that the morphospecies concept can use to identify distinct species?
distinct morphological differences
How can you use phylogenetic trees to infer how viruses have spread?
establish order of events and similarities
Phylogeny
evolutionary history of a group or species
Phylogenetic Tree
graphical summary of the evolutionary history of a group or species
Polyphyletic Group
group that does NOT contain the most recent common ancestor
Monophyletic Group
include all descendants of common ancestor -group that contains the most recent common ancestor plus all and only all of its descendants
Paraphyletic Group
include some but not all descendants of a common ancestor -group that contains the most recent common ancestor, but NOT all of its descendants
Polyploidy
increase in chromosome number relative to ancestors
Genetic Distance
infers relationships among taxa based on genetic similarity
How would you test for coevolution from two phylogenies (for two different groups of species)?
make a phylogenetic tree
Cladistics
naming schemes that are based on evolutionary relationships
Vicariance
new barrier separated pre-existing populations -allopatric speciation
Tokogeny
relationships among individuals of the same species
How is the branch support for clades on the most parsimonious tree determined using bootstrap?
resample characters with replacement to estimate support for each branch in inferred phylogenetic tree
Symplesiomorphy
shared, primitive character state
Independent Evolutionary Lineage (Convergent Evolution)
similarity between species that is caused by a similar, but evolutionary independent, response to a common environmental problem.
Homology
similarity due to common ancestor -all synapomorphies are homologous -symplesiomorphies can be homologous
Analogy
similarity not due to common ancestry -reversal -convergence
What types of groups are species concepts trying to recognize?
species
Interbreeding
successfully producing fertile offspring
What does "interbreeding" mean in the context of the biological species concept?
successfully producing fertile offspring. It means theres one species if they are able to interbreed.
Why do the phylogenetic species concept and the morphospecies concept focus on differentiating between comparable individuals rather than differentiating between all individuals?
there are too many differences between all individuals than there are in comparable individuals
Autapomorphy
unique derived character state
Coevolution
when natural selection occurs and produces adaptations in both species involved
Reversal
-"back mutations" -DNA changes back to an ancestral form -If a reversal has occurred, then similar traits are not homologous and do not qualify as synapomorphies
Maximum Likelihood
In addition to evaluating the best trees implied by a parsimony analysis, most researchers analyze their data sets with a phylogenetic method that computes a probability or likelihood that alternative trees are supported by the data
Dispersal
Individual(s) cross barrier -allopatric speciation
From a phylogenetic perspective, which kinds of groups should be named in our taxonomic classification system: monophyletic, paraphyletic, or polyphyletic? Why?
Monophyletic groups should be named because they include all the descendants of a common ancestor
Which of the three species concepts can be applied to asexual linages?
Morphospecies Concept and Phylogenetics Species Concept
Which of the three species concepts can be applied to sexual lineages?
Morphospecies Concept, Phylogenetics Species concept and Biological Species Concept
What kinds of characters can be used for phylogenetic analysis? What are some requirements for characters used in phylogenetic analysis?
Possible Sources of Characters are; Morphological Structures, DNA sequences, Chromosome numbers, behavior, and chemical compounds -Requirements for characters are; they must be Independent, Heritable, and Variable
Why might the three different species concepts provide different answers on the number of species in a given lineage?
They take different factors into account
Bootstrap Support
a computer creates a new data set from the existing one by repeated sampling
Synapomorphy
a homologous trait that is shared among certain species and is similar because it was modified in a common ancestor -shared, derived traits
Parsimony
a logical way to distinguish homology from homoplasy and identify synapomorphies